Flash Communication: Properties and Applications of a Pentavalent Bromoantimony Lewis Acid

While normally reluctant
toward oxidation, SbBr3 can
be oxidized with 3,4,5,6-tetrachloro-1,2-benzoquinone (o-chloranil) in the presence of a Lewis base like the bromide anion
or triphenylphosphine oxide (PPh3O) to form the tetrachlorocatecholate
(catCl) derivatives [SbBr4(catCl)]− ([2-Br]−) and SbBr3(catCl)•OPPh3 (2•OPPh3), respectively. Structural, spectroscopic,
and computational data indicate that the SbBr3(catCl) fragment is similarly, if slightly less, Lewis acidic than
the previously reported SbCl3(catCl) fragment.
The SbBr3/o-chloranil system, as well
as its previously reported counterpart SbCl3/o-chloranil, were tested as Lewis acid catalysts for C–O bond
metathesis and polycarbonate depolymerization. These results identified
SbX3/o-chloranil pairs (X = Cl, Br) as
simple main-group platforms for C–O bond cleavage chemistry.